Rare Earth Disilicate Coating for Gas Turbine Oxidation Resistance
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Solution Overview
Problem
Current protective coatings for high-temperature turbine components, such as silicon nitride and silicon carbide, face challenges including erosion due to silica scale formation and diffusion of oxygen, which limits their operational temperature and durability, especially in gas turbine engines.
Innovation Solution
A protective coating system comprising a rare earth disilicate environmental barrier coating layer and a porous rare earth monosilicate thermal barrier coating layer, with metal silicate infiltration, applied to ceramic matrix composite substrates to enhance thermal resistance and prevent cation migration, allowing operation up to 1500°C (2800°F).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tantalum oxide alloyed with lanthanum oxide is used as environmental barrier coating, then oxidation resistance is improved, but oxygen diffusion occurs resulting in SiO2 layer formation below the coating
Solution Approach 1:
The patent changes the chemical composition parameters of the environmental barrier coating by using rare earth disilicate materials (such as Yttrium Disilicate, Y2SiO5) instead of traditional tantalum oxide alloys. This compositional parameter change eliminates the oxygen diffusion problem while maintaining oxidation resistance, as the rare earth disilicate coating does not permit oxygen diffusion to the substrate.
Solution Approach 2:
The patent employs a composite coating structure consisting of multiple layers: a base rare earth disilicate environmental barrier coating layer and a surface treatment layer forming a thermal barrier coating. This composite structure combines the oxidation resistance of rare earth disilicate with the thermal barrier properties of the surface-treated layer, achieving both protection against oxidation and thermal stress while preventing oxygen diffusion.
2Reliability
If rare earth silicates are used to form protective coating on silicon based substrate, then erosion resistance is improved, but coating composition is limited due to interaction with substrate
Solution Approach 1:
The patent applies local quality by creating distinct functional zones within the coating system: the base layer uses rare earth disilicate for oxidation and erosion resistance, while the surface treatment layer provides thermal barrier properties. Each layer has specific compositional characteristics optimized for its particular function, allowing the coating to resist erosion while maintaining compositional flexibility through the layered approach.
3Duration of action of stationary object
If high temperature barrier coating is applied to prevent silica scale formation, then component durability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by first forming the rare earth disilicate environmental barrier coating layer on the substrate before performing the surface treatment to create the thermal barrier coating. This sequential approach, where the EBC layer is applied and cured before the thermal barrier layer is formed, simplifies the manufacturing process by breaking down the coating application into distinct, manageable steps rather than requiring complex simultaneous deposition.
4Reliability
If coating layer is made dense to prevent oxidation, then oxidation resistance is improved, but thermal barrier performance decreases
Solution Approach 1:
The patent segments the coating into two distinct functional layers: a base rare earth disilicate environmental barrier coating layer that provides oxidation resistance, and a surface treatment layer that forms a thermal barrier coating with controlled porosity for thermal performance. This segmentation allows each layer to be optimized for its specific function without compromising the other, resolving the contradiction between density for oxidation resistance and porosity for thermal barrier performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The coating system significantly increases the operational temperature of turbine components, reduces erosion, and provides a uniform, oxidation-resistant barrier, improving engine efficiency and extending component lifespan while minimizing cooling requirements.
Implementation Method 1
There is also a need for a diffusion coating that will prevent migration of cations out of a silicon-based substrate
Implementation Method 2
a thermal barrier coating layer including a porous rare earth monosilicate material having a metal silicate material infiltrated within at least a portion of the pores
Implementation Method 3
Evaporation of silicon hydroxide from ceramic surfaces and erosion of ceramic caused by high speed combustion gases passing over ceramic surfaces leads to the loss of ceramic material
Data Source
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AI summary
A protective coating system includes a turbine engine component substrate formed of a ceramic matrix composite material, an environmental barrier coating layer including a rare earth disilicate material formed directly on the substrate, and a thermal barrier coating layer including a porous rare earth monosilicate material having a metal silicate material infiltrated within at least a portion of the pores formed directly on the environmental barrier coating layer.